Chinese leaders fired the Communist Party chief of the restive city of Urumqi and the regional police chief Saturday following deadly protests that inflamed ethnic tensions.
The official Xinhua news agency did not give a reason for the removal of party head Li Zhi, who was replaced by Zhu Hailun, and Liu Yaohua, head of the regional public security department, who was replaced by Zhu Changjie.
Thousands of mainly Han Chinese took to the streets of Urumqi this week, demanding better security following a series of bizarre attacks involving syringes.
The protesters also criticized authorities for being too slow to punish those responsible for July's ethnic violence between mainly Muslim Uighurs and Han Chinese that killed nearly 200 people in the capital of the Xinjiang region.
Officials say five people were killed Thursday during demonstrations.
Saturday, Urumqi returned to an uneasy peace under the watch of thousands of security forces, who patrolled the streets and set up security checks throughout the city. There were reports of troops using tear gas to break up a group of people gathered near city government offices.
Urumqi's deputy mayor, Zhang Hong, told reporters Friday that 21 Uighurs had been detained, including four who were indicted for alleged involvement in the syringe attacks. State media reported the majority of attack victims were Han Chinese.
China's Public Security Minister Meng Jianshu was also quoted by state-run Xinhua news agency as saying ethnic separatist forces were to blame for the nearly 500 needle attacks.
Official media reports say only 89 people showed obvious signs of being pricked by a needle, and no deaths, poisonings or infections have occurred.
The Uighurs see Xinjiang as their homeland and resent the millions of Han Chinese who have come to the region in recent decades.
The Uighurs say the Han have unfairly benefited from the riches of Xinjiang, a strategically vital Central Asian region with significant oil and gas deposits.
The Han believe the Uighurs are unfairly favored by set-aside quotas for government jobs and university placements.
Some information for this report was provided by AFP, AP and Reuters.